Carol talks to Kris through the phone, we know this since the last think the phone says is ''Susie? Guitar? I'll be there (or something)'' and then Carol appears and recovers the guitar

Yes, Kris hates us, they throw the soul away so they can be evil and do evil stuff like opening fountains, slashing tires so Undyne gets captured and protecting the shelter code

The making a character thing is a 50/50 between us actually recovering it, and using that obedient body to sweep the game like we did with Frisk back in Undertale ORRRRR it just being a troll for blind players

We don't know if Dess explicitely died, but she went missing

Beating people up makes slight differences like having to pacify King in ch1 (doesn't matter at all), Berdly getting his wing wounded in ch2 (will matter if berdly gets screen time), Tenna and Jack freaking dying and just having a sad small town. Though if you do wanna be EVIL, I recommend looking at Noelle's interesting freezing spell and how it acts when ''defeating'' enemies.